you can defenatly overdose on c02. it happend to me the day after i instaled my diyco2. what happened was i got a major ph drop. drop of almost 1 point, then two days later i had a small algea bloom. but im pritty shure it happend because i didn't have any plants to take care of the c02. befor you install it you should get a co2 test kit to monitor how much it puts into the tank. DON'T get the tetratest co2 test kit. it sucks. its cheeper but it sucks.

__________________

__________________
there once was a kid named colin. he looked just like a gorilla. his name wasn't magilla, because it was colin.

I don't think you've thoroughly researched CO2 injection, or you'd know about the Kh/pH chart used to measure CO2 levels.

Injecting CO2 doesn't cause algae either...in fact, it prevents it. Its also possible to inject too much CO2 using DIY, even on a 46 gallon tank. However as long as your Kh is over 3degrees, it's a slim chance of putting too much CO2 in. Fish can tolerate much higher levels of CO2 than what teh plants need. Plants don't need much more than 30ppm of CO2...I've had fish in 85ppm of CO2 and none suffered any ill effects, however that didn't make the plants grow any better.

__________________Former advisor and planted tank geek...life's moved on though.

I have read several articles (the one you mentioned included) but the biological aspects of fish care (chemical balances, etc.) are new to me, so I'm trying to make sure that I have all my ducks in a row before I go injecting any CO2.

When it's all new, it's hard to know what's important and what's not. I believe I skimmed the page you referenced because I was looking for construction info at the time. Now I'm past that and into the implementation mode. It's definately more helpful for that phase.

I'll check the chart and grab a KH test if that should suffice and start reading.

Thanks for all the helpful suggestions. I can't talk about megabytes and megahertz all day long, but I'm pretty quiet when it comes to PH/KH

malkor, unless black udder already has a kh test kit, there going to have to go buy a test kit anyways. so if your going to get a test kit, why not get one that measures exactly what your dealing with to make things easier.
and exess co2 can cause algea blooms.

__________________
there once was a kid named colin. he looked just like a gorilla. his name wasn't magilla, because it was colin.

I have no real idea on PH - it's between 7-7.2, but that's a big swing. The tank has been setup for over a year and it's running well now, so I know whatever the PH is, it's consistent. Problem is, that if I'm going to inject CO2, then PH of 7.0 means i'm getting 15ppm of CO2 (which has to be bogus) and even 7.2 is around 9.5. The lighting is not that strong (40w - but expect the 96w to show up tomorrow).

Question is - would it be worthwhile to invest $30 in a Hanna digital ph tester? That should deliver a more accurate result of ph, right?

Also, I do have 1-2ppm of phosphates in the tank which I believe will skew the KH test.

Suggestions, thoughts? I know you guys answer these questions a million times (I've been going thru the history).

malkor, unless black udder already has a kh test kit, there going to have to go buy a test kit anyways. so if your going to get a test kit, why not get one that measures exactly what your dealing with to make things easier.

If I understand it correctly, all the CO2 kits on the market only measure CO2 indirectly, using KH & pH (They might call it something else in the kit, to make it more appealing, but it is just KH & pH yoiu are getting). So there is no need to buy one of those expensive kits .... unless there exists a kit that directly measures CO2.

Also, I do have 1-2ppm of phosphates in the tank which I believe will skew the KH test.

You have KH of 90 & pH of 7.0 without any added CO2? That would translate to a CO2 of 15ppm. Clearly impossible with room air CO2 of 3ppm.

Your problem is not with the pH test ... but the phosphate. All those CO2/KH/pH tables assumes you have no other buffers apart from HCO3. When you add in a second buffer (PO4), you invalidate the whole equation & can no longer trust the CO2 reading from the charts (or from the run of the mill CO2 test kits either).

We had a thread going about this 2nd buffer problem. http://www.aquariumadvice.com/viewtopic.php?t=43891
Some one suggests simply estimating CO2 on pH change alone. There are lots of pitfalls with this approach .... I would wait for someone with actual experience dealing with the same buffer combinations as yours to chime in....

malkor, unless black udder already has a kh test kit, there going to have to go buy a test kit anyways. so if your going to get a test kit, why not get one that measures exactly what your dealing with to make things easier.
and exess co2 can cause algea blooms.

Because a Kh test kit is needed to know your Kh levels, which are important. Why limit yourself to what you can test by buying a CO2 test kit, when you'd still need a Kh test kit for other reasons.

I will defer to jsoong as to the effects of phosphate buffering on pH measurements. I do, however, have a few words to add on CO2 levels supposedly influencing algal growth. In my plant-only grow-out tank I've experimented with very high levels of CO2 (via pressurized injection) to see if they have any noticeable effect on plant growth rates. My conclusion is that growth rate gains end at around 30-35 ppmCO2. Anything beyond that appears to have little effect at all on the flora in the tank and is essentially wasted. I have never had an algae outbreak due to excessive CO2, and I've run it up 70-80 ppm to replicate the natural environment of some of the Cryptocorynes I keep. IME almost every algae outbreak can be ascribed to a macronutrient imbalance, most often nitrates.

__________________
“There is something in the quality of a good translation that can never be captured in the original.”
-William Gibson

k. so i did alot of reading. (spent about an hour) and i must say i was incorect in my asumption that co2 can cause algea blooms. . in other words i was very wrong. sory malkore. i just asumed that because i had an algea bloom right after the c02 rise that the co2 caused it. thank you for teaching me a wise lesson about doing reading.
but im still sticking to the fact that its better to just get a co2 test kit, if your injecting co2. you can always reverse the chart and use ph and co2 to find kh. then youll know the kh and a more acurate view of the co2.

__________________
there once was a kid named colin. he looked just like a gorilla. his name wasn't magilla, because it was colin.

You can't really "reverse the chart" .... unless you can have a way of directly measuring CO2 - which I don't think the CO2 kits can do.

You can get a pretty good estimate of KH if you can measure pH accurately in water equlibrated with room air (the CO2 level is known in that case). Actually, measuring CO2 level in room air equlibrated water is a pretty good way of seeing how accurate your tests are. If you get screwy results <as Black Udder seems to be getting>, then something is amiss.

BTW - I am not sure if the 2 ppm of PO4 will account for all the CO2 level discrepency we saw, 2 ppmPO4 vs 90 of KH seems a bit low to account for a 5 fold error in CO2 level. It is possible that there are other buffers present, or that there are errors in measuring the pH or KH.

Also, even if CO2 kit does actually measure CO2...it won't help you in non-CO2 injected tanks. Normal levels for CO2 are about 2-3ppm...regardless of pH or Kh...thus reversing the chart won't tell you squat.

You can do as you like Foma...but I stand by my advice that a pH and Kh test kit are the smarter route.

__________________Former advisor and planted tank geek...life's moved on though.

It doesn't require phosphates to interfere with KH test kits. Any other acid, such as fulvic, humic, or nitric acids will be titrated giving false high KH readings...this is why using peat filtered water won't allow accurate CO2 level determinations. CO2 test kits are even worse. Common CO2 test kits, such as LaMotte's, uses a base (sodium hydroxide) to neutralize all the acid in the test water sample. This assumes all the acid is carbonic acid from CO2. Anyway, sodium hydroxide is added until all the acid(s) are neutralized and the pH is raised to 8.3 which is signaled by the color change of phenolphthalein. So you can see that the CO2 test kit is more susceptible to interference than the KH test kit...any acid or base already present in the sample with be "counted" as CO2. Collecting and performing the test itself can also cause some of the CO2 to "outgas" and not reflect a "true" CO2 reading. The nomographic method is more accurate (using the pH and KH)...a point the LaMotte clearly makes is that the CO2 test kit they sell is for "field" estimates only and that the nomographic method is suggested for greater accuracy. Note also that is takes a lot of phosphate to effect KH test kit interference...at least 20 ppm to distort CO2 levels significantly. As always with CO2 injection, let your plants and fish be the true measurements of CO2. Never place too much faith in any test kit reading.

KH registers 1 now (1 drop turns blue, 1 more drop turns yellow) From Tap = 17GH registered 7 drops (125.3 ppm) From TapPH might be 7.3-7.4 (I did the high PH test for giggles and it's an amber) From Tank
The normal PH registers light blueKH from the tank registers 4 drops or 71.6
This would yield a possible level of CO2 of around 4.8
Phosphates from the tank and the tap were both less than 1ppm

Does this sound more in line?

I must say all this information is both overwhelming but fascinating to read.

DIYCO2 is assembled now...new light is in place (96w pc) and filter is the fluval 4 plus (internal filter).